A series of strange deaths shake ancient Tallinn. While these tragic events incite all kinds of superstitions, Melchior is mandated to solve this enigma.

Melchior's wife witnesses an attack and a young man's is saved, but the victim has no memory of who they are or how they got to Tallin. A ring leads Melchior to the night brotherhood.

In 15th-century Tallinn, the apothecary Melchior Wakenstede is a learned man with a keen sense of observation. So, when a knight is found murdered, the governor of the city entrusts him with the task of flushing out the assassin.